Well, That Escalated Quickly...

SteveA said:

And if you torqued a chilled iron cam to anywhere near 50 ft/lbs that would be the source of the breakage. Limit is 20 ft/lbs.

Interesting idea to save your self the effort of taking off the head, but when you said it was last built in 2005, as if it was just last year, I chuckled a bit.

Don't you think it would be interesting to see how your valves are holding up on their seats after 17 years, and maybe change the valve stem seals?

I confess I have stripped my race engine enough times since 2015 that I wouldn't even think to do it that way, but of course, with through bolts I couldn't anyway!.

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I made a judgement call and I will own it. It is riding season and the engine was performing fine other than the cam issue. I saw no reason to pull the head.

Yup, my bad on over torquing the chilled iron cam. I was not even aware that the cam was chilled iron, and there was no warning of lowering the torque of this nut accordingly. The shop manual that I have doesn’t even list a torque on the cam nut. Expensive lesson, but such is life…

The new one is nitrided EN40B, so I felt comfortable with that torque on a 3/4” thread.

I don't know about you, but 2005 sure feels like yesterday!! LOL!!

Now, what if I were to tell you that my Combat motor has not been opened up since 1975?? The horror - lol!!

Well,
I’m mightily impressed with your knowledge, organisation and planning in getting the job done with so little fuss.
I know if it had of been me, I would have mucked about, spent a heap more money, taken months to get back on the road and ending up doing a complete rebuild for no real purpose.
Even better, irrespective of whether it was your fault or not in over-tensioning the cam nut, by fitting the different camshaft, you can have an improved bike through a happy acciden.
Good one,
Alan

I think I read here, some time ago, a conversation about partially dismantling an engine in this manner.

Of course, people lined up on one side or the other, and there was very little convincing the other side to agree.

If I ever have to get in and have a look again, I have already convinced myself that in using this method the biggest drawback would be a POSSIBLE oil weep.

grandpaul said:

I think I read here, some time ago, a conversation about partially dismantling an engine in this manner.

Of course, people lined up on one side or the other, and there was very little convincing the other side to agree.

If I ever have to get in and have a look again, I have already convinced myself that in using this method the biggest drawback would be a POSSIBLE oil weep.

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Yes, I kind of expected people to be polarized on this kind of repair. Definitely not for everyone's taste. More of a demonstration of the fact that it can be done. Ultimately, each to their own.

Oil leaks were one of my primary concerns as well, hence great care was taken in cleaning and prepping all sealing surfaces. It was an oil-tight engine before, and so far, so good.

Fingers crossed...

Chill cast iron is still about the best material to make a cam from, but it is now expensive to do so even for some motor manufacturers. Yes, I had quote from China and it was eye wateringly expensive and the MOQ was massive. EN40 is very good, but must be nitrided correctly, this was clear when I had one (not ANIL item) sectioned and tested at a UKAS facility. I predict that some out there are using EN40 cams that have 'failed' but don't know it, nor will they as I suspect they have the correct hardness separation with the followers fitted.
I use a chill cast cam that is of a design that PW did before his passing, it runs on radius followers and has so far covered 16K miles. On a recent base gasket replacement the cam and followers were still showing the grind pattern on the rubbing faces, so I was amore than happy with that. This set up was also tested on the dyno so doesn't get treated kindly.

Madnorton said:

...This set up was also tested on the dyno so doesn't get treated kindly.

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Some people have no idea that depending on the dyno operator (who typically also operate the motorcycle being tested), they typically run through the test with a lashing that 98% of bike owners would never DREAM of doing to their bikes.

(just so's ya knows)

That is a chilled iron cam, good follower wear characteristics but they do not hold threads well and break easily. The nut can not be torqued to a high enough pressure to keep the sprocket from slipping without a generous coating of red locktite. I will not use a chilled iron cam on any of my builds. Jim